Eli5 Can someone simply prove me use of combination in binomial expansion

Question

Like when you expand (x+y)²= (1,1)x² + (2,1)xy + (1,1)y². Its obvious in this case but when the calculation gets complicated its hard to fit in your mind

In: 0

Answer 1

Google and Wiki can cover. It follows a pattern.

[https://en.wikipedia.org/wiki/Binomial_theorem](https://en.wikipedia.org/wiki/Binomial_theorem)